Particle Size Dependence Research Articles

Milling Duration Influence on Strontium Hexaferrite Technological Characteristics

Fine powders of strontium hexaferrite are widely used in powder metallurgy for the production of permanent magnets resistant to atmospheric oxygen and high working temperatures. Obtaining powders with predefined technological characteristics in minimal time and with minimal energy consumption is an actual problem of powder metallurgy. The paper provides the results of experimental studies of technological characteristics of strontium hexaferrite powder (SrFe12O19) during milling in a beater mill. Mechanical milling of coarse strontium hexaferrite was carried out in the mill with the system of rotating beaters for 120 minutes without and with the creation of a pseudo fluidized bed. The fluidization was formed by a perpendicular constant and alternating magnetic field with induction gradients of 150 and 210 mT/m. Average particle size and powder bulk density dependencies from milling time were studied. Experimental data show that milling with the formation of a magneto fluidized bed allows intensifying the process. Beginning from 70 minutes, the dependencies of average particle size and bulk density come to almost asymptotic behavior making further milling rather ineffective. Carried out research allows choosing optimal milling duration for obtaining the required average particle size.

A numerical study of the effects of ambient temperature and humidity on the particle growth and deposition in the human airway

A numerical study was conducted on the effects of ambient temperature and humidity on the transportation of sodium chloride particles (100 nm-1 μm) in a human airway model ranging from the nasal cavity to bronchi. A mucus-tissue structure was adopted to model the mass and heat transfer on the airway surface boundary. The temperature and humidity distributions of the respiratory flow were calculated and then the interaction between the particle and water vapor was further analyzed. It was predicted that the particle size grew to the ratio of 5–6 under subsaturation conditions because of hygroscopicity, which shifted the deposition efficiency in opposite directions on dependence of the initial particle size. However, the particles could be drastically raised to 40 times of the initial 100 nm diameter if the supersaturation-induced condensation was established, that was prone to occur under the cold-dry condition, and consequently promoted the deposition significantly. Such behavior might effectively contribute to the revitalized coronavirus disease 2019 (COVID-19) pandemic in addition to the more active virus itself in winter.

Synthesis and characterization of carbon-coated Cu-Ni alloy nanoparticles and their application in conductive films

In this paper, an efficient fabrication route is presented for carbon-coated Cu-Ni alloy nanoparticles (Cu1-xNix@C NPs; x = 0–1.0) by means of electrical wire explosion under methane gas. The Cu-Ni binary system, which is considered to be an ideal isomorphous system, has carbon growth controllable by tuning the atomic fraction of Cu and Ni with largely different carbon solubility. As the Ni content increases, the average particle size and carbon layer thickness increase. It is notable that the carbon layer is very thin, <2 nm, regardless of the core size for pure Cu@C NPs. On the other hand, as the Ni content increases, the particle size dependence of the carbon-layer thickness becomes significant and the carbon layer is obviously tunable from amorphous to crystalline form. The high-temperature oxidation stability of Cu1-xNix@C NPs is enhanced with increasing Ni content due to the higher thermal stability of carbon layers with greater thickness and high crystallinity. The conductive films were prepared using screen-printing of paste containing Cu1-xNix@C NPs and the electrical resistivity was mapped according to the Ni content. The temperature stability of the sheet resistance and activation energy of oxidation for the conductive films increase with increasing Ni content.

Lies, damned lies, and turnover rates

A Rayleigh distribution of particles exposing (1 1 1) surface populations is consistent with the particle size dependence of the turnover rates of the electrochemical reduction of dioxygen catalyzed by a platinum cathode.

Adsorption of Cetylpyridinium Chloride at Silica Nanoparticle/Water Interfaces (I): Dependence of Adsorption Equilibrium on Particle Size.

In the current work, a size-effect model was developed to describe the particle size-dependence of adsorption at solid/liquid interfaces. A parameter, ΔQad, was introduced, defined as the change of the product of the solid/liquid interfacial tension and the molar volume of solid surface components caused by adsorption. The model predicts that with a decrease in particle radius (r), the saturation adsorption amount per unit area (Γm, mol/m2) decreases, while the change of the adsorption equilibrium constant (Kad) is determined by the ΔQad, namely, it decreases if ΔQad > 0 but increases if ΔQad < 0. There exists a critical r at which the saturation adsorption amount per unit mass (Γmg, mol/g) attains a maximum. In addition, the adsorption of cetylpyridinium chloride (CPyCl), a cationic surfactant, on silica nanoparticles with different r (ca. 6-61 nm) values was determined at 298 K and pH 9, showing an obvious size-dependence. With a decrease in r, Kad and Γm decrease, indicating a decrease in the affinity of silica particles toward CPyCl. The size-dependent adsorption data can be well described using our model. Adsorption can affect the molar volume of the solid surface phase, which plays an important role in the size-dependence of adsorption. This work provides a better understanding of the size-dependent adsorption phenomenon at solid/liquid interfaces.

Investigation of particle size effect on antibacterial activity of copper ferrite using polyvinylidene fluoride (PVDF) and silicone rubber matrices

In this research, the dependence of CuFe2O4 particle size on the antibacterial properties was investigated. The morphology of the particles was controlled in the presence or lack of sucrose as a novel capping agent. Antibacterial properties of the CuFe2O4 nanoparticles were evaluated using the PVDF or silicon rubber matrices. The crystalline structures of the CuFe2O4 were confirmed by X-ray diffraction (XRD) patterns. The prepared nanostructures were more dissected using field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR), and vibrating sample magnetometer (VSM). Eventually, the copper ferrite particle size effect in PVDF and silicone rubber matrices on the antibacterial activity was investigated. The obtained results revealed significant antibacterial properties for the particles. It was found that decreasing particle size would improve antibacterial properties within both polymeric mediums. This research presents novel separable antibacterial magnetic nanostructure suspended in novel media.

Dependence of Particle Size and Shape of Polyaniline Nanoparticle on the Time of Ultrasonic Irradiation Reaction

Dependence of Particle Size and Shape of Polyaniline Nanoparticle on the Time of Ultrasonic Irradiation Reaction

On the lattice dilation of palladium nanoparticles and a new methodology for the quantification of interstitials

In contrast to the expected behavior for metallic nanoparticles (NPs) where a contraction of the lattice parameter occurs as the crystal size decreases, palladium NPs experience both lattice contraction and dilation. Such dual behavior has not been discussed in detail so far but it is of paramount importance given Pd is widely used in catalysis, electrocatalysis, gas sensors, and many other areas, and all these applications are strongly affected by structural change at the NP surface. Herein, we address the issue investigating both lattice contraction and dilation of Pd NPs synthesized by chemical reduction and also by compiling several results already published in the literature. It was found that when the synthesis is carried out in the absence of a substrate, dilation of the unit cell was detected; in contrast, if the synthesis is carried out in the presence of a substrate (carbon and RuO2), lattice contraction is observed. Lattice dilation was ascribed by the incorporation of interstitial atoms, such as H, C, O, which is suppressed on supported catalysts likely by a spillover effect from the metallic phase to the substrate, thus yielding to lattice contraction. Furthermore, we propose a new methodology to assess the total variation of the lattice parameter in the case of lattice dilation taking into consideration the expected contracted values for nanosized particles. To illustrate the importance of such new approach, it was possible to show a particle-size dependence of the carbon solubility on Pd nanostructures based on literature data.

Airborne particulate matter distribution in urban green space is size-dependent

While the spatial distribution of airborne particulate matter (PM) inside and outside urban green spaces is affected by many environmental factors, the mechanism of the inside-outside difference (IOD) remains unclear. Particle size is an important attribute of PM, but the relationship between IOD and particle size is unknown. By measuring the IOD and external environmental conditions of 188 green spaces in Beijing city (China), we found that the distribution of PM inside and outside green spaces is size-dependent. According to the particle size dependence of PM, they can be divided into three classes (i.e., PM1, PM1−5, and PM5−25). The motion characteristics of particles, influence of environmental factors, and their coupling effect might be responsible for this size dependence. This study highlights the importance of size dependence in understanding the mechanism of PM distribution in urban green space through field experiments and puts forward a new concept of particle size classification that might be more suitable for actual environmental conditions and can support the improvement of related models.

Quantitative evaluation of surface roughness for granular materials using Gaussian filter method

This contribution proposes a methodology to measure the surface roughness of granular materials using the Gaussian filter. Artificially generated rough surfaces with known root mean square roughness (Sq) combined with the spherical shape are analysed to determine the optimum cut-off wavelength (σ∗) adopted in the Gaussian filter. Considering a combined dependency of Sq and particle size (D) on σ∗, an empirical regression equation is derived to describe their relationship. The regression equation is further found to be applicable for granular materials including glass beads and natural sand grains with irregular base shapes. To implement the proposed Gaussian filter method into practical use, a detailed guideline is given to determine Sq including the selection of representative measurement area. Finally, quantitative comparisons of Sq are made to distinguish the difference between the proposed method and motif method.

Synthesis, growth, physio‐chemical and Hirshfeld surface analysis of guanidinium l-glutamate single crystal

In the present work, a novel Guanidinium l-glutamate (GLG) optically transparent single crystal has been synthesized and grown by slow solvent evaporation method for the first time is reported. Single crystal X-ray diffraction demonstrates that the GLG crystallizes in non-centrosymmetric monoclinic crystal with P21 space group. The different functional groups present in the grown crystal were found by Fourier transform infrared analysis. The optical properties of the grown crystal such as absorbance, laser damage threshold have been studied. The bandgap energy of the crystal was found to be 4.66 eV. Thermal properties of GLG crystalline samples were analyzed using Thermogravimetry/Differential Thermal Analysis. Further, the material is characterized by Hirshfeld surface analysis to analyze and interrupt the intermolecular interactions of GLG. Scanning Electron Microscope (SEM) studies were carried out to study the surface morphology of the grown crystal. By using Kurtz-Perry powder technique second harmonic generation and particle size dependency was carried out for the title compound.

Emissions of polycyclic aromatic hydrocarbons from primitive e-waste recycling: Particle size dependence and potential health risk

Polycyclic aromatic hydrocarbons (PAHs) with great health implications have been identified as important by-products during primitive obsolete electronics (e-waste) recycling activities. Their distribution patterns and human exposure levels are highly particle size dependent, but have not been adequately examined due to the lack of emission data. The present study was conducted to address this issue by measuring the emissions of PAHs from thermal treatment and open burning of typical e-waste pieces. The emission factors from thermal treatment and open burning of plastic casings were 3.15 × 104–1.56 × 105 and 4.22 × 103–1.96 × 104 ng g−1, respectively, with 6.37 × 104–2.17 × 105 and 1.98 × 103–2.68 × 103 ng g−1 for printed circuit boards, respectively. Low-molecular-weight PAHs predominated the total PAH emissions in both procedures. Particulate PAHs contributed the most emissions in thermal treatment, but gaseous PAHs predominated in open burning. Generally, the size distributions of particle matter and PAHs were characterized by a unimodal shape peaking at 0.56–1 or 0.32–0.56 μm. Most PAHs especially high-molecular-weight ones were found on fine particles. Absorption appeared to be the main mechanism at emission sources and re-distribution of PAHs may have occurred between particulate and gaseous phases during progressive dispersal from combustion sources. High cancer risk (7.23 × 10−4) was incurred for e-waste recycling workers via inhalation and dermal absorption, mostly attributed to the exposure of fine particles. Improved techniques are needed to reduce potential health risk for e-waste recycling workers and residents living in adjacent areas.

A study of uncoated and coated nickel-zinc ferrite nanoparticles for magnetic hyperthermia

The paper describes how to arrive at the required characteristics suitable for the study of magnetic hyperthermia in a nanoferrite. The composition selected for the study, Ni0.60Zn0.35Fe2.05O4 was synthesized by sol-gel process with an adequate control on its particle size using a chelating agent, polyethylene glycol (PEG). Nanoparticles with mean particle sizes in the range 3.6–8.2 nm were obtained by annealing the as-prepared powder at different temperatures. Identification of single phase spinel structure, particle size determination and magnetic properties of all the samples were made available with X-ray diffraction, Transmission electron microscopy, and Vibration sample magnetometer. The single domain nature of the nanoparticles was established from the particle size dependence of the coercivity. The superparamagnetic behaviour of two annealed samples having a mean particle sizes 3.6 nm and 4.4 nm was established from the temperature dependence of the field cooling and zero field cooling magnetization curves. The observed higher blocking temperature (below room temperature) for smaller particles was attributed to interactions between the particles in the powder samples. The effect of interparticle interactions on heating efficiency was examined by comparing the specific absorption rate (SAR) of nanoparticles dispersed in water at different concentrations. The higher zeta potential values of citric acid coated nanoparticles were pronouncing their long time stability in water with increased SAR and cell viability as compared to their uncoated counterparts. Interestingly, the results of water based citric acid coated nanoparticles assure that the material would be suitable as magnetic mediator for magnetic hyperthermia application.

Signature of Transition between Granular Solid and Fluid: Rate-Dependent Stick Slips in Steady Shearing.

Despite extensive studies on either smooth granular-fluid flow or the solidlike deformation at the slow limit, the change between these two extremes remains largely unexplored. By systematically investigating the fluctuations of tightly packed grains under steady shearing, we identify a transition zone with prominent stick-slip avalanches. We establish a state diagram, and propose a new dimensionless shear rate based on the speed dependence of interparticle friction and particle size. With fluid-immersed particles confined in a fixed volume and forced to "flow" at viscous numbers J decades below reported values, we answer how a granular system can transition to the regime sustained by solid-to-solid friction that goes beyond existing paradigms based on suspension rheology.

Dependence of Soot Primary Particle Size on the Height above a Burner in Target Ethylene/air Premixed Flame

ABSTRACT McKenna burner providing premixed, laminar, steady flat flame is widely used in the combustion community. The ethylene/air flame with equivalent ratio of 2.34 is considered as one of the target flames for the development and calibration of optical diagnostics of soot particles. In this work, the accurate soot particle sizing in dependence on the height above a burner was performed using the methods of transmission electron microscopy and laser-induced incandescence. It was found, that shielding co-flow gas type and rate together with small variation of the height of stabilization plate in flat premixed flame burner is not influenced on the center flame temperature and on the soot particle size measurement results. Also, the small variation of the velocity of the cold gas in the 5% range at the same equivalence ratio is not influenced by the results of flame temperature and soot particle size measurements. From the other side, the variation of the burner stabilization plate configuration and material of the sintered plate results in the essential differences of the measured values. The accomplished data analysis resulted in a reliable dependence of soot size in the target flame on the height above a burner, which can be applied for validation of soot formation models.

Preparation schemes of crushed coal for combustion in fluidized bed boilers using a gravity separator

The low concentration of nitrogen oxide during coal combustion in fluidized bed furnaces is due to the limited proportion of primary air in the combustion zone. The schemes applied for the preparation of crushed coal are mostly for the use of coal breakage screens with a fixed maximum particle size in the mixture. The primary air flow is limited to the conditions of the fluidization of the bed and can be reduced only by reducing the size of the particles fed into the furnace. With a constant particle size and lower boiler loads, the proportion of primary air and thus the concentration of nitrogen oxides in the flue gas increase. The use of separators to change the particle size has never been considered, since it is a priori assumed that the separators cannot provide the required disperse composition of crushed coal. To assess the possibility of using separators in the schemes of preparing crushed coal for combustion in a fluidized bed and to determine the necessary separation boundaries, variants calculations were carried out in respect to the coal preparation scheme for boiler No. 9 of the Novocherkasskaya hydro-power plant. It is shown that the disperse composition of the fine separation product in the gravity separator with overturning shelves along the 5 mm boundary is identical to the disperse composition of crushed coal obtained in the scheme with a screen and crusher. The dependence of the maximum particle size of crushed coal on the separation boundary of the separator is given. It is shown that in the scheme of preparation of crushed coal for combustion in a fluidized bed, replacement of screens with gravity separators will not lead to violation of the requirements for the dispersed composition of crushed coal. At the same time, the proposed replacement allows you to quickly change the maximum particle size of crushed coal during operational activity and thereby to maintain the optimal fraction of primary air when the boiler load changes.

Determination of ferrimagnetic and superparamagnetic components of magnetization and the effect of particle size on structural, magnetic and hyperfine properties of Mg0.5Zn0.5Fe2O4 nanoparticles

The fine-tuning of magnetic parameters and the identification of different magnetic phases are essential for the effective utilization of magnetic nanoparticles. In this work, we aim at controlling the magnetic parameters of Mg0.5Zn0.5Fe2O4 nanoparticles by varying the particle size and to determine magnetic phases using three analytical techniques having different operating time scales: VSM, ESR, and Mössbauer spectroscopy. Single-phase cubic spinel structured Mg0.5Zn0.5Fe2O4 nanoparticles were prepared by the sol-gel auto-combustion route and calcinated at 200, 300, 500, 700, and 900 °C. The cation distribution and structural parameters obtained from the Rietveld analysis had an insignificant variation with the calcination temperature. From the TEM analysis, an increase of the average particle size from 5 to 38 nm and widening of the particle size distribution with the calcination temperature were found. The saturation magnetization increased from 25.6 to 43.7 emu/g with the particle size due to the reduction in the magnetic dead layer thickness. The coercivity decreased from 128 to 31 Oe and the blocking temperature from 76 to 38 K with the particle size and these variations are explained in terms of surface anisotropy and dipolar interactions. Ferrimagnetic, superparamagnetic, and paramagnetic components of magnetization were deconvoluted by the curve fitting of room temperature VSM data. The ferrimagnetic component increased from 56% to 74% and the superparamagnetic component decreased from 37% to 20% respectively with the particle size. The ESR and Mössbauer spectroscopy also identified the ferrimagnetic and superparamagnetic components in the samples and their variations with the particle size were found to be in agreement with that of VSM. Thus, the variation of magnetic parameters in correlation with the particle size offers the possibility of fine-tuning the magnetic parameters of nanoparticles by adjusting the particle size. The deconvolution of magnetic phases using the three analytic methods revealed the coexistence of ferrimagnetic and superparamagnetic components of magnetization in Mg0.5Zn0.5Fe2O4 nanoparticles. Also, this deconvolution unveiled the particle size dependence on the emergence of inhomogeneity in magnetic phases of the samples.

A Model Structure for Size-by-Liberation Recoveries in Flotation

This communication presents a model structure for the flotation recovery of middling particles (10–90% liberation). Fourteen datasets from the literature were studied (galena flotation), which involved different flotation systems and operating conditions. The flotation responses allowed the model flexibility to be evaluated under a range of recovery profiles. The modelling results showed that galena recovery can be characterized by the interaction between a linear function and a concave function (e.g., Gamma model), to account for the liberation and particle size effects, respectively. Liberation also impacts the location and dispersion of the recovery dependence on particle size. The proposed model structure showed there was adequate flexibility with five parameters, leading to adjusted coefficients of determination ranging from 0.863 to 0.998 for the studied datasets. Thus, an alternative approach for modelling the recovery of middling particles is proposed, which represents the liberation and particle size dependence with a few parameters.

An investigation of the mixed water/formamide solvent on the synthesis of cadmium nitroprusside particles and its behavior in the electrochemical sensing of isoniazid

Size-controlled cadmium nitroprussides, with particles in the micron meter or submicron size range (0.050–1.15 micron), (CdNPs) were prepared from total and varied compositions of water and formamide solvent in the complexation reaction of cadmium and nitroprusside ions. Four analytical systems (CdNP-1, CdNP-2, CdNP-3, and CdNP-4) were set up. The coordinated materials were investigated by spectroscopic and analytical techniques such as Raman spectroscopy, ultraviolet-visible spectroscopy (UV-Vis), X-ray diffraction (XRD), scanning electron microscopy (SEM), and cyclic voltammetry (CV). The CVs of the modified graphite paste electrode with CdNP-1, CdNP-2, CdNP-3, and CdNP-4 (10% m/m) exhibited a defined redox pair with formal potential (Eθ′) = 0.63 ± 0.02 V (ν = 20 mV s−1; KNO3 1.0 M). The dependence of particle size on the isoniazid electro-oxidation was verified by CdNP-3 and CdNP-4 microparticles.

SYNTHESİS AND STUDY OF MESOPOROUS TİTANİUM-SİLİCATE CATALYSTS

The paper presents the results of studies on the development of synthesis methods and study of the properties of a catalyst based on titanium silicalite for the synthesis of MEKmethylethylketone. Samples of titanium silicalite were synthesized with different ratios of the starting reagents - tetraethoxysilane and tetrabutoxysilane. Tetra-n-propyl ammonium hydroxide was used as a structure-forming agent. The data of IR spectroscopy and powder Xray diffraction made it possible to establish the effect of the amount of the structure-forming agent on both the structure and morphology of the titanium silicalite obtained. The main product is a mixture of TiO2 and amorphous SiO2. The dependence of the average particle size on the initial ratio of the initial reagents is established: with an increase in the initial molar ratio of the reactants, a change in the size of the catalyst particles is observed. The main indicators of the catalytic activity of the catalyst samples obtained at different initial ratios of reagents are compared. The carried out physicochemical studies on the synthesis of titanium silicalite made it possible to establish the composition that provides the maximum selectivity for the formation of methylethylketone. Keywords: methylethylketone, mesoporous titanium-silicate catalyst, catalytic activity.